FCL Effect of DC Superconducting Cables in Unsteady State

DC superconducting cables for railway systems connected between substations have been developed. If the length of the superconducting cable is long enough, the superconducting cable is expected to have an effect of a resistive type fault current limiter (FCL) by the transition of the superconducting state and the normal state due to overcurrent than the critical current. Therefore, the simulation model of a direct current system with superconducting cables was constructed and the behavior of a superconducting cable was analyzed. And, there is a possibility of deterioration of critical current in a superconducting cable due to the aging and unexpected stresses since a superconducting cable is assumed to operate for long term. Then, the behavior of a deteriorated superconducting cable in the unsteady state was also analyzed. The analyzed results suggest that the 3000-m-long superconducting cable has the FCL effect and the temperature distribution assuming operation at liquid nitrogen does not affect the FCL effect. Furthermore, influence of the local deterioration, which has a potential to damage a superconducting cable in the unsteady state, could be estimated using this constructed model.